Spherical plain bearings generally include inner and outer ring members wherein the outer ring member has a spherical concave interior surface that defines a cavity therein and wherein the inner ring member is disposed in the cavity and has a spherical convex surface that is complementary to, and is dimensioned to match, the interior concave surface of the outer ring member. In the assembled bearings, the concave and convex surfaces slide over each other to define the bearing surfaces or “load zone.”
A lubricant may be provided in the load zone of the bearing to minimize wear and to enhance rotational characteristics. In some spherical plain bearings, a lubrication groove may be provided in one of the sliding surfaces. The lubrication groove is a recess from the sliding surface within which a reserve of lubricant can be disposed. The recess is open to the other sliding surface, which can be contacted by the lubricant. As the second surface slides over the first, lubricant is carried between the sliding surfaces to lubricate the bearing. A conventional lubrication groove has sharp edges at the sliding surface of the ring member on which is it formed. The sharp edges tend to wipe lubricant from the surface as one ring member moves relative to the other ring member, thus inhibiting lubricant from lubricating the bearing.
Also in some spherical plain bearings, seals may be incorporated in an attempt to retain the lubricant in the load zone and to prevent or at least limit the flow of lubricant from the load zone. These configurations have a natural tendency to be easily removed after wear has occurred (either inadvertently or intentionally) or to be difficult to position in place initially. Furthermore, these sealing members are often undesirably located on the edges of the ring members of the bearings and adjacent to the contact surfaces of the load zone. When located on the edges of the ring members and adjacent to the contact surfaces of the load zone, the sealing members are easily damaged and/or dislodged, which makes it harder to maintain the seal to retain the lubricant in the load zone. Furthermore, the wiping function of the seal (ability to spread the lubricant on the bearing surface proximate the area at which the seal contacts the bearing surface) may be compromised.